


Mercy

by nekotachis



Series: Commissions [1]
Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Anal Play, Bondage, Dubious Consent, F/M, Restraints, Sea Monsters, Tentacle Sex, Trans Dedue Molinaro, Trans Male Character, Vaginal Play, mermaid
Language: English
Status: Completed
Published: 2021-02-20
Updated: 2021-02-20
Packaged: 2021-03-17 00:35:21
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,173
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29584545
Author URL: https://archiveofourown.org/users/nekotachis/pseuds/nekotachis
Summary: “So, you are…” Dedue trailed off. What was the proper terminology to call a girl who lived in the sea?“Flayn, a siren who has lived in these depths for a long time. And you are a human, who has not lived here as long as I have. What is your name?”He ran over all the fairy tales in his head. He couldn’t think of a single one that said you would be cursed for eternity if you gave a siren your name.“Dedue.”Dedue is a sailor who meets Flayn, a sea maiden, and falls for her. When he's thrown overboard, she saves him, only to have her way with him in return.
Relationships: Flayn/Dedue Molinaro
Series: Commissions [1]
Series URL: https://archiveofourown.org/series/2173545
Comments: 1
Kudos: 12





	Mercy

**Author's Note:**

> This was an anonymous commission.
> 
> I use all terminology for Dedue's genitals (pussy, cunt, cock, clit). There is vaginal and anal play.

Settling down came easy to Dedue.

He thought it would be a struggle. The rest of his friends had seemed restless; Sylvain had settled up north, more work to be done. Dimitri reigned with Felix at his side. Mercedes tolled with the homeless and orphaned, Annette moved on to teach, and Ashe, Ingrid…Well, everyone was looking forward to their next challenge.

Dedue had drifted back to Duscur in the post-war peace. His home called out to him, a place to rest and find renewal, and it wasn’t long before he settled off the western coast. The home he dwelled in he built himself, the large garden in the front well tended year round. Fish and meat cured in the crisp sun. 

His pride and joy was his boat, small and without a sail. Dedue had never been much of a sailor, but he had come to appreciate the solitude of rocking out in open waters. 

-

The sun was cresting over the horizon in a soft morning fog that drifted off the ocean. The good weather was promising, gulls dipping low along the horizon. Fish was in his future - he had a mean craving for stew and he wasn’t ready to wait a moment longer. Dedue rolled up his pants and sleeves and pulled his boat off the shore.

He rowed his way out to open water until his house was no more than the size of a speck. He threw the net overboard, pulled his shirt off, lied back, and waited. A cool breeze blew over his bare chest, and he inhaled the salty air. Today was going to be a good day. He could feel it.

-

Dedue shot up abruptly, reaching out to steady himself. The boat was stuttering and leaning port side, the net tugging against the ties that held it to the boat. He whipped his head around, his hair slapping against his face - the sky was clear still, the sun at its zenith, but the breeze from before had stopped. The waters were still.

With another jolt, his boat rocked harder. He rocked the opposite way to counter it. _Something must be caught_. There was no other explanation for such a racket. Dedue knew there were large creatures that lived along the peninsula - marlins and whales - but nothing that wouldn’t decimate his tiny net.

Fighting against the rocking, Dedue heaved the net up. It was heavier than his normal load, and his shoulders and arms burned as he worked the net and it’s contents up and over the gunwhale. Silvery fish and seaweed spilled on the deck, washing over his bare feet. Something was trapped in it, screaming and writhing like no animal Dedue had ever seen or heard before.

Frantic, he took out his knife, slicing through his netting to help free the trapped creature. An arm that looked vaguely human flailed out, and Dedue ducked to narrowly miss it. With a final slice, the creature broke free, sputtering.

Dedue was very familiar with the myths and folklore of Duscur. He knew the stories of wood nymphs that made the flowers grow, of the gods and goddesses that came together to make the Duscur peninsula. He heard plenty of stories of sailors seduced by sea maidens, dragged under by giant squids, torn apart by massive crabs. But all those stories had just been stories to him - tall tales to tell him to not stray too far from home.

Sprawled on his deck was the most perfect example of a sea maiden Dedue had ever seen. Her top half was human, just like in the stories. Her hair was sea foam green, her skin pale as if it had never seen the light of day. Her body transitioned into sleek, dark green scales, splitting off into tentacles of different sizes with different tipped ends. The sea maiden’s breasts were small and perky, her nipples the palest pink Dedue had ever seen. And her face - her face was sweet and innocent, her eyes green and wide in shock.

Dedue stood in silence, staring as his chest heaved. This was no crest beast. She was far too beautiful to be such a thing. The gears in his head turned, trying desperately to process what he was seeing.

“Oh, thank you -”

Dedue panicked. It not only looked like a woman, but it spoke like one too, her voice as crisp as a gull’s cry. Terrified, he squat down to her level, heaving her lithe body overboard with a giant splash. Her skin was cool against his body, and he shivered. It was a refreshing contrast to the sun beating down on his bare back.

“Hey!” It squealed.

Dedue dropped down on his bottom, peering overboard. The sea maiden was staring at him, her face serene. Her hair fanned out around her, flowing with the motion of the waves that splashed against her face.

“You should warn someone before you do such a thing,” she said, as if in casual conversation.

Dedue blushed - even if she was a monster, it was rude to just toss something overboard. 

“Can you speak?” she asked, frustrated.

He scoffed, incredulous. He should be asking her that.

“What are you?” Dedue said. His steady voice did not bely his fear. 

“Are you always so rude?” 

Dedue jolted and frowned. He had been called lots of things, but never rude. “I apologize,” Dedue said softly. She was right; it was rude to ask what someone was. “And I apologize for tossing you in so carelessly.”

Her grin was pleasant. Inviting. Nothing haunting the ocean depths could have such a cute demeanor. “It is fine! You were doing me a favor. Being caught up in your net was truly terrifying, but my true home is here in the sea.”

“So, you are…” Dedue trailed off. What was the proper terminology to call a girl who lived in the sea?

“Flayn, a siren who has lived in these depths for a long time. And you are a human, who has not lived here as long as I have. What is your name?” 

He ran over all the fairy tales in his head. He couldn’t think of a single one that said you would be cursed for eternity if you gave a siren your name.

“Dedue.”

-

On every clear day that Dedue sailed out, Flayn had always managed to be nearby. Dedue was much more cautious with his nets, and Flayn was more conscientious of his boat. He noted that he was often the only vessel coming and going. It had been years since he last saw another ship sail near his waters. 

With the way Flayn spoke to him - an endless stream of questions and information - he figured she must be lonely. She was fascinated with “his kind”, obsessed with his thick legs and the coarse hair that covered them. She loved to hear about his adventures on land, and even more so she loved to listen to his stories of his culture and people. 

Dedue couldn’t stop himself from falling for her. He blushed at how her small hand fit into his, the burn of desire at seeing the contrast of his skin on her small body when she let him touch, and how the deep oceanic green of her scales complimented his complexion. And where he thought she would be cold and slick, she was warm, like a stone in the sun.

Most of all, it had been years since he last had someone listen to him with such rapt attention. He planned for longer and more frequent fishing outings, just for the opportunity to see her eyes go wide in excitement at his stories.

-

It was the first overcast day of the season, the winds gusting strong against him as he pulled his boat into the waters the same way he did every day. The sky matched the color of his hair, diluted and dreary, and salt water sprayed painful pellets across his arms and face. A thread of dread formed in his heart, but he pushed it away. Weather was nothing to fear, and he had been in far worse situations.

Of course, knowing that Flayn was out there comforted him.

He struggled to steer his boat, the choppy waters fighting against him. He reminded himself that what mattered was that he needed food. Bad weather couldn’t deter him from feeding himself. Still, it was like the sea was ready to pick a fight, pushing back against every row. 

The further out he went, the choppier the ocean became. Fat, foamy waves battered against the side, gaining in strength until they sloshed over the gunwhale and into his lap. Dedue stopped rowing, letting the waves and wind carry him as he collected his thoughts. Clearly this weather was worse than he expected, but he was too far out to row his way back in. He would tire before he could reach shore. 

In the distance, like a beacon, he spotted Flayn. Her head bobbed with the waves and she looked unaffected by the unkind weather. 

“Flayn!” Dedue shot up, waving his arms. The boat rocked violently, and he struggled to stay upright. “Flayn! Please!”

A strong wave hit the side of his little boat, and he fell over, catching himself before falling face first into the water. When he looked back up, Flayn was gone.

On wobbly legs, he attempted to stand. The ocean was empty - not even gulls took risks in weather like this. It was like a blow to his psyche, the crushing feeling of helplessness crumpling his insides.

Another violent wave crashed over the boat, and Dedue toppled over into the ocean’s depths.

-

Dedue’s arms and legs wheeled and kicked, churning the dark waters to white foam. He panicked, unable to orient himself. Seaweed wrapped itself around his body, slimy and cold, and he bit down a scream. Despite genocide and war, this would be his end, tossed overboard on a stormy day when he just wanted dinner.

His lungs were burning, but he wasn’t ready to give up. Dedue propelled himself forward, hoping it was the right direction. He didn’t have much time left; his arms and legs felt like molasses, their energy sapped, and his head was fuzzy as if he was drifting off to sleep. Swimming was hopeless. He made no progress. The best he could do was say a prayer and come to terms with his life. He closed his eyes, succumbing to the push and pull of the currents.

Dedue gasped, nerves firing for one last desperate attempt at life, but instead of water air filled his lungs. Something foreign wiggled his way into his throat, and he took another gasping breath in. His animal brain took over - fighting took over fleeing, and he blindly reached around him, kicking and grabbing for whatever was trying to strangle him.

More _things_ slithered around his limbs like snakes, suspending him. Dedue’s heart pounded in his chest, the thrum of his pulse battering against his skull. He was trapped and at the mercy of some creature. Ruefully, he thought he should have paid better attention to his bedtime stories.

“Please calm yourself, Dedue.” A sweet voice rang out, chiming like a bell. It sounded familiar. “You are safe here with me, all for me. Do not be afraid, my handsome sailor.”

 _Flayn_. It must have been her. She told him that nothing but her had lived in these waters for centuries. Was her friendship just a ruse to steal him away to her lair and eat him up like a rack of ribs?

A soft lullaby reverberated through his body, as if the sound was being carried by the water itself. It was something ancient and foreign, and Dedue couldn’t tell what she was saying, but he could _feel_ it, like hot tea warming his cold bones. His body felt weightless, and more tendrils wrapped around him to cradle his body. He couldn’t speak, not with this thing in his mouth, and his thrashing calmed until he was pliant and weak. His arms and legs were pulled away in different differections, but his body refused to struggle. Dedue felt weightless, as if he was a kite barely tethered to the ground.

Flayn’s bright face entered his vision, as brilliant as the noonday sun with an infectious smile. It should comfort him, but apprehension built underneath his stupor. 

“What a fortuitous day for me, to have you all to myself once and for all.” 

A frightening barbed tentacle rose in front of him, and he groaned around the thick intrusion in his mouth. 

With a flick of the tip, it sliced through his shirt like paper, exposing his broad, scarred chest to her. The water was even colder with his body bare, and his nipples pebbled so hard it hurt.

“Oh, how splendid!” Flayn squealed with delight. Human hands joined the roaming tentacles, her tiny fingers pinching at a nipple before sliding down to appreciate the curves of his abdomen. He wished he could turn his head just a bit to appreciate her small hands on the broad expanse of his belly. He had fantasized about it for so long and now here, like this…

His pants slipped free, whisked away by another tentacle.

“Oh, oh my.” Flayn gasped, and Dedue heard a hint of arousal in it. “How absolutely perfect.”

More appendages reached over him, exploring him like hundreds of tiny fingers. Underwater, they felt slick with some sort of goo, radiating an unusual warmth. Some pulsed like a beating heart, wandering up the inside of his thighs to probe at the junction of his leg and groin. Something was biting at his neck, small nips with sharp teeth, as suckers laid across his chest and belly, pulsating movements pulling at the sensitive skin. Smaller appendages no bigger than garden snakes crawled down his back, sharp points dragging while the slick tentacles soothed the soreness.

It felt like a hundred hands on him all at once. Warm, slick, pinching, sharp - it all attacked him at once. A sucking tentacle wrapped around his neck, pulling at the skin over his jugular. He was being touched in every erotic place on his body all at once, and some new ones he didn’t even knew had existed before. 

Several tendrils slithered up the back of his head, entangling themselves in his hair before abruptly pulling his head back. A moan rumbled in his chest, unable to break free, and his pussy throbbed with a ferocious heat. A bleb of fluid dripped from his hole, suspended in the water, and he clenched his fists and braced himself.

Flayn’s laughter shook through him, as if it traveled through the hundreds of appendages that surrounded him. The vibrations only enhanced his arousal, and he wanted to sob. “I see that you like what I have to offer?” 

Dedue decided he loved what she had to offer. He feared it and he craved it. He gurgled around the appendage in his mouth, aching and needing more. Each tentacle was working separately to break him down piece by piece, and her song had lulled him into an aroused stupor. 

All the limbs were getting closer to his core, faster and quicker. They pulled at him and poked at him, but never settled where he needed it the most.

He felt fingers comb through his coarse pubic hair, and he whimpered. 

Flayn hummed in curiosity, “Even hair down here! You truly are covered in it.” 

Dedue jolted in his bonds when he felt her fingers slide over his cock. The thick jut of it slipped between her fingers before springing out, and his face flushed. Did she understand human anatomy? Could she even understand what she was doing to him?

Dedue was unable to bend and look, but he could feel her exploring his pussy. Her fingers pushed between sensitive folds, prodded against his hole before sliding back to tenderly slip against his other. She pried him open, and he imagined she was looking at him. The water felt cool and soothing against his heat, but he wanted to close his legs in shame. More fluid dripped out of him and Flayn caught it with her fingers, wiping it in his pubic hair.

“Already, you are so wet. You truly do love my body, dear Dedue.” Flayn whispered in awe. “Are you able to be a good boy and take me?” 

Small tentacles no thicker than several fingers prodded at his entrance, and Dedue gurgled around his breathing tube. Dedue had never been called a _good boy_ before, and it poked at his belly like a heated spear. He wanted to take it, wanted to be good.

They pushed into his hole, slow and steady, pulsating and pushing against his soft inner walls. He could feel Flayn watching, her hungry gaze transfixed on his stuffed hole. Gently, the appendages inside of him began to explore, pushing and pressing on every tender spot inside of him. All Dedue could do was pant, succumbing to the invasive prodding of Flayn’s body. Her fingers followed suit, feeling the hot, stretched skin where her tentacles entered him before slipping her own finger inside.

Surely, Dedue was going to die like this, pleasure coursing through his body like live electricity.

“Just like that, my good boy. You are so perfect, and so handsome.”

The best response Dedue could give was to succumb, to let himself be used and touched. His pussy bared down on the tentacles inside of him, and in return they pulsed and filled, stretching at his tender, swollen entrance. 

“I know that you can take more.” Flayn cooed, her voice distant over the rush of blood in Dedue’s head. A dreamy pleasure jolted through him as a tentacle probed at his cock, lifting the hood and attaching a sucker to the head. “You are the only one for me.” 

A hefty tentacle prodded at his ass. He’d never been taken like this before, but Flayn is gentle with her touch. It slid deep inside of him, pulling him open and probing deep. Flayn sighed heavily, her hands leaving his sex to rest over the growing mound of his belly. 

Like this, Dedue was full to the brim, complete, overflowing. Flayn’s hands explored every peak and valley of his body - skipped over the sensitive tissue of an old burn, dug into the muscle of his chest, traced over his open mouth and scarred face. His body was a blur, a dream, and he could barely breath against the push and pull over the morphing appendages that surrounded and filled him..

The sucker on his cock sped up as if it sensed his arousal, and both tentacles began to fuck inside of him. He was stretched so wide around them, his arousal a chalice full of molten silver pouring out to seep into every crack and crevice his insides.

“Now, now, Dedue. Calm yourself, I am here to help you,” Flayn said, her hands settling on the swell of his pecs. “Does a good boy like you want to finish?”

Dedue would scream if he could, and his chest rose and fell with quick panting breaths. It is not a want or a need - he was going to come whether he liked it or not.

Flayn pulled away, and he felt his heart wishing she would come back. “A good boy will help me finish first.”

The tentacle in Dedue’s mouth began to slip out, and he coughed against it, gasping. Instead, something wet and slick met his face. 

“Show me how much you love me, and then I will reward you in kind.” Without another option, Dedue probed up with his tongue. It felt like a familiar shape, deep and warm with a hole in the middle, but lacked the same folds and bumps. It was briny with a hint of sweetness, and he thrust his tongue in deeper so he could lick up into the empty space.

Above him, Flayn sighed, pulling his face closer to her body with a pair of tentacles. Her sighs and moans were sweet and heavenly, and he worked at her hole leisurely. He felt her out with his lips, mouthing at the ridged entrance before shoving his tongue back inside. As her body moved, so did her many tentacles, pulling and releasing as if the nerves were misfiring. 

She rode against his mouth, her hole rocking against him. The rim caught against his nose, and she thrusted down harder, his mouth encasing her sex. Something inside her swelled out, peeping through the entrance of her sex, and Dedue captured it between his lips without a second thought, sucking and lapping at the protrusion.

“Oh, oh! Perfect, perfect!” Flayn cried out, and Dedue felt encased by her body. “Do not stop, that is so good, my good boy.” She gasped, and Dedue moaned up into her. “My love, my love, keep going.”

His face is pushed against her, his breath stolen from him as he ate at her ravenously. Her cries reach a fever pitch, and Dedue is lost in the smell and taste of her. It’s new and unlike anything he had ever experienced before. And his own orgasm is so close, the throbbing and sucking of his own body persisting at a painfully steady rate. 

A splash of fluid hit his face as Flayn yelped. Dedue coughed against it, catching as much as he could with his open mouth as the rest spilled off of him.

Immediately, Flayn pulled away, and the breathing tube slithered back down his throat. Dedue felt her pulling him against her chest, and through his aroused haze he could see her pupils blown wide and her face graced with the most delicate blush. She shifted him like he was weightless, despite her being half his size, and cradled him in the hammock of her body.

“Perfect, Dedue. You deserve a reward, my sweet boy,” Flayn whispered in his ear before increasing the intensity of the pulsing inside of him. She worked at him with a fury, her tentacles fucking his holes twice as fast. While he ate her out, his arousal had waned, but now it met him head on, gripping him in a vice.

Dedue’s body shook as he strained to hump and thrust against her. His cock throbbed and trembled as another sucker joined the first one. 

“You can let go, my love.” Flayn buried his head in the gentle swell of her chest, and he could hear her heart beat in a steady rhythm. His skin felt like it was burning up along the places they touched, and he cried out weakly. 

“Oh, my dear, do not cry, just let go for me.”

His orgasm swelled inside of him like a wave, bursting from his belly to ripple out onto his limbs. Flayn gentled him through it, his body jolting against his bonds. His holes clenched against the intrusions, and they pitifully pushed back, milking him. Pleasure seeped into his bones, and he blissfully wondered if it would ever end. Stuffed full of Flayn’s tentacles, he thought he might burst at the seams. He’d never been so full in his life.

Dedue’s body released, relaxing back into Flayn’s cradle. Her voice was a soft murmur, like a lover’s gentle kiss. He was exhausted and worn out, and as each appendage pulled out of him he felt his eyes go heavy with sleep. The lullaby from earlier started again, and all was right in the world. 

-

The sand was hot underneath his body when he woke up, squinting against the blaring sun. The sky was clear and cloudless, and seabirds pranced along the shore, oblivious to Dedue. His little boat rocked gently on the calm water, not tethered to anything and not a single dent in its side.

Sitting up, he ran his hands over himself. His shirt was gone, and he was sure he left with it on this morning. His pants were on backwards, and he was soaking wet. Pitifully, he scrubbed at his face, dusting off stuck on sand as best as he could. 

He took a moment to scan his body. He felt like he had run laps around the island, his arms and legs sore from tension. There were strange marks covering his body: hickeys and scratches reaching every part of him. Out of curiosity, he looked in his pants - everything was as it should be, at least, but he couldn’t ignore how empty he felt.

Sighing, Dedue recalled his day. It had almost felt like a dream. He swore he took the boat out today, but maybe he fell asleep reading one of the novels Ashe had sent him. He shivered at the thought. He would have to write to Ashe and tell him to stop sending him so many of them since they seemed to be clouding his mind.

Dedue sat for a bit, watching the horizon.

The horizon is empty.

**Author's Note:**

> Thank you for such a fun challenge! I've never written tentacle sex, let alone Dedue or Flayn before! It was a pleasure to work with you.
> 
> I can be found on [Twitter](https://twitter.com/nekotachis)


End file.
